Multiple trace recorder



April 23, 1968 G. R DAVIS MULTIPLE TRACE RECORDER Original Filed Feb. 8, 1965 GLEN R. DAVIS ATTORNEYS United States Patent 3,380,068 MULTIPLE TRACE RECORDER Glen R. Davis, Tulsa, Okla., assignor to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware Continuation of application Ser. No. 430,880, Feb. 8, 1965. This application June 26, 1967, Ser. No. 649,051 2 Claims. (Cl. 346-49) This is a continuation of application Ser. No. 430,880, filed Feb. 8, 1965.

This invention is an improved method for producing photographic records of electric impulse variations. The method is of particular value where a plurality of traces are to be produced on a single recording, the method providing for traces clearly distinct one from the other.

While the method of this invention is applicable to curve identification in many situations, it is particularly appropriate for use in making seismogram records. In these records, the energy responses to be studied are converted to a pattern of essentially parallel wiggle-trace lines. Frequently as many as ten wiggle-traces appear on a single photographic record. In more sophisticated systems, twenty-four or as many as forty-eight traces appear. It can be appreciated that when a considerable amount of overlapping of traces occurs it is diflicult for the human eye to follow individual traces. With the advent of analog-to-digital convertors, it is diflicult to program a scanner so that a single trace will be followed throughout a record with the record not being sidetracked by interference traces or by coordinate grids.

When the method of this invention is used, each curve of the record can be produced having its own characteristic pattern, usually a dashed line with the length of of the dash and the space between dashes varied from curve to curve but consistent within a curve.

Seismograph and many other kinds of photographic records of electric impulse variations are usually produced by passing the electric impulse through a galvonometer containing a mirror. The electric impulse, by the use of magnetism is made to produce a torque which twists the mirror. A light source, ordinarily an incandescent lamp directs rays toward the mirror and these rays, in a narrow path, are reflected to a light-sensitive moving tape. The swing of the mirror thus produces a curved line on the tape. Where a series of curves is to be recorded simultaneously, a plurality of galvanometers is employed, each having a mirror to reflect rays in a different pattern, normally from a common light source.

In this invention, an individual source of flickering light is used for each galvanometer and each light source uses an electric current of differing frequency to produce a different but constant frequency of flicker. When reflected by the individual galvanometers, this method results in wiggle-traces on the film which have characteristic dot or dash frequencies for each trace.

In order to provide the clearest pattern of dashes or dots, a light source having the shortest possible lag between the start and finish of each electric current cycle and the start and finish of the light flash is employed. Thus, a gas discharge-type light source, such as the ordinary fluorescent light is preferred over an incandescent light source.

The invention will be better understood by reference to the accompanying drawing in which FIGURE 1 is a schematic representation of an apparatus which may be employed in practicing this invention; and FIGURE 2 is a sample of a photographic record resulting from the use of the method of this invention.

In the drawing electrical impulses are sent from a source 11 through a line 13 to a galvanometer represented generally as 15. This galvanometer has a mirror 17 between two coils 20 and 22. The mirror 17 is contained within a light impenetrable shield which conveniently is made of an electrically conductive metal grounded at 27. Also within the shield 25 is the light source which conveniently is a gas filled fluorescent type light source grounded at 33 and operated by alternating current from the line 36. Light sour-cc 30 is separated from the mirror 17 by a shield 31 having an opening 32 therein.

As shown, the source of alternating current is a generator 39 which is grounded at 42 and which is driven by rod 45 attached to bevel gear 48 which in turn is operated by bevel gear 50 which in turn is driven by the rod 53 and motor 55 which is supplied with electric current from leads 57 and 60 which are connected to a suitable source of current not shown. Also driven by rod 53 are other bevel gears 63, 66, 70, 72 and 75 which, as shown, are gears of the same diameter as 50. These bevel gears drive the other bevel gears 77, 80, 82, 84 and 86. It will be noted that these latter bevel gears differ in diameter from each adjacent bevel gear. Preferably no two of the gears 48, 77, 80, 82, 84 and 86 are of the same diameter and preferably they are chosen and arranged for maximum differences in size, preferably between each set of two adjacent cognate beveled gears of this set. Each of these gears 77, 80, 82 84 and 86 is fastened to a rod and thus is operable to drive alternating current generators 88, 90, 93, 96 and 99, respectively. As can be seen, each of these generators supplies current to lamps 101, 103, 107, 109 and 111, respectively. These lamps, as well as light impenetrable shields 112, 113, 114, 115 and 116 and galvanometer mirrors 117, 118, 119, 120 and 121 are contained within the light impenetrable shields 123, 125, 127, 129 and 131. As shown, these latter shields, like shields 25, may be made of an electrically conductive metal which can provide grounding for the light sources and the galvanometers. As can also be seen, these galvanometers 123 through 131 may be electrically connected by leads 133, 135, 137, 139 and 141 to sources of variable electric current 143, 144, 146, 148 and 150, respectively. As shown, these sources of variable current are geophones which contact the earth 152. Depending upon the strength of the variable currents emanating from sources 11, 143, 144, 146, 148 and 150, the leads 13, 133, 135, 137, 139 and 141 may be supplied with amplifiers or other means (not shown) for insuring that a current strong enough will reach each galvanometer to result in twisting of the mirrors 7, 117, 118, 119, 120 and 121. In the case of geophones, the varying electric currents may be produced in response to sound waves reaching each geophone, for example, by reflection from subterranean formations of sound waves, represented by lines 156, emanating from seismic source 155, e.-g. explosive, compression generator, etc.

Light from sources 30, 101, 103, 107, 109 and 111 passes through openings 32, 102, 104, 106, 108 and in shields 31, 112, 113, 114, and 116 along paths illustrated by letters A, B, C, D, E, and F, respectively, and is reflected from mirrors 17, 117, 118, 119, and 121 respectively, along paths designated A, B, C, D, E and F, respectively, to the photographic device 157 which is provided with reels of photosensitive tape 158 which conveniently may be operated by the motor 159. Impringement of the light rays from the lettered paths upon the sensitive paper results in tracings similar to those shown in FIGURE 2. It will be noted that the tracing result of each lettered path differs from its adjacent tracing in the length and frequency of its dashes and the spacing between the dashes. Gears 63, 66, 70, 72, 75 and 50 being of the same size and being driven at the same rate; gears 48, 77, 80, 82, 84 and 86 being of different sizes, at least when one of these gears is compared to its adjacent gear, these latter gears revolve at different rates. Thus, the frequency of the alternating current produced by generators 39, 88, 90, 93, 96 and 99 varies among these generators, at least among adjacent generators. Thus, the flickering light produced by each of the lamps 30, 101, 103, 107, 109 and 111 varies in frequency and the reflected light rays A, B, C, D, E and F also vary in duration and frequency. The photosensitive sheet is moved in the device 157 at a rate suflicient to separate individual flickers of light. Thus, the tracings A, B, C, D, E and F have the variable dashed character indicated and can be easily followed throughout the record even when the tracings cross and recross each other. Of course, if desired, the electric frequency variations between the various lamps can be accomplished by radio circuitry oscillators as well as by the mechanical generators illustrated.

It is claimed:

1. A system for simultaneously producing a photographic record of the variations in a plurality of electric impulses comprising photosensitive tape means, an individual source of flickering light for each of said electric impulses, galvanometer means for each of said electric impulses having a rotatable mirror for converting the variations in the respective electric impulse into variations in the rotational position of the mirror, means for operating the light sources to produce flickering light beams including means supplying electrical power to said light sources having different frequencies for the light sources providing adjacent beams on said tape means, the light beam from each source being reflected by the corresponding mirror to impinge upon said tape means and produce thereon a visible trace for the respective electric impulse, at least the adjacent light beams on said tape means having different frequencies of flicker, and means for moving said photosensitive tape means at a speed sufficient to produce dashed traces corresponding to each of the plurality of electric impulses, the dashes of which are characteristic of the frequency of flicker of the light source.

2. The system of claim 1 wherein said light sources are electrically operated gas discharge lamps.

References Cited UNITED STATES PATENTS 1,842,968 1/1932 Horvath 346-33 X 2,775,503 12/ 1956 Peterson 346-109 2,937,915 5/1960 Peterson 346109 2,958,010 10/1960 Carter et a1. 346109 X 3,042,922 7/1962 Ledbetter 346109 X RICHARD B. WILKINSON, Primary Examiner.

JOSEPH W. HARTARY, Assistant Examiner. 

1. A SYSTEM FOR SIMULTANEOUSLY PRODUCING A PHOTOGRAPHIC RECORD OF THE VARIATIONS IN A PLURALITY OF ELECTRIC IMPULSES COMPRISING PHOTOSENSITIVE TAPE MEANS, AN INDIVIDUAL SOURCE OF FLICKERING LIGHT FOR EACH OF SAID ELECTRIC IMPULSES, GALVANOMETER MEANS FOR EACH OF SAID ELECTRIC IMPULSES HAVING A ROTATABLE MIRROR FOR CONVERTING THE VARIATIONS IN THE RESPECTIVE ELECTRIC IMPULSE INTO VARIATIONS IN THE ROTATIONAL POSITION OF THE MIRROR, MEANS FOR OPERATING THE LIGHT SOURCES TO PRODUCE FLICKERING LIGHT BEAMS INCLUDING MEANS SUPPLYING ELECTRICAL POWER TO SAID LIGHT SOURCES HAVING DIFFERENT FREQUENCIES FOR THE LIGHT SOURCES PROVIDING ADJACENT BEAMS ON SAID TAPE 